]May 20, 1910] 



SCIENCE 



799 



ever to winter injury. Peach yellows is thought 

 by the writer to be a contagious disease, though 

 the germ has never been discovered. It behaves in 

 many ways, though not in all respects, like pear 

 blight. For example, when the pear blight germ 

 is absent from a locality there can be no blight 

 no matter how favorable conditions may be. In 

 the same way peach yellows has a distinct range 

 in the northern and eastern part of the United 

 States. It has increased its area rather rapidly. 

 No matter what the conditions may be of soil, 

 climate, method of culture, fertilizer, etc., when 

 the yellows reaches a district it attacks the 

 orchards. 



Pear blight has its ups and downs. Some years 

 the conditions are favorable and some years un- 

 favorable for the spread of the disease. Peach 

 yellows behaves in the same way. Pear blight 

 spreads from colonies or infection centers. Peach 

 yellows behaves in exactly the same way. 



Pear blight lives over winter in the " hold- 

 over " cases, this becoming the new infection 

 centers each spring. With peach yellows every 

 case is a hold-over till the tree dies. 



Pear blight can be inoculated artificially by 

 introducing the germ or the diseased tissues. 

 Peach yellows can be inoculated by introducing a 

 bit of living tissue. Both diseases are unknown 

 elsewhere in the world, although their host plants 

 are foreign to this country and are cultivated 

 widely over the earth. 



Pear blight was mistaken for frost injury be- 

 fore its bacterial nature was discovered. 



We know peach yellows as a distinct disease, 

 through a number of definite symptoms. The dis- 

 tinctive symptoms of peach yellows are, first, the 

 premature, red-spotted fruit; second, wiry or 

 bushy vertical sprouts of a peculiar character. 

 Peach yellows has also certain leaf symptoms, 

 such as yellowing and curling. These symptoms 

 are also shared by the disease known as " little 

 peach." The leaf symptoms, however, are not 

 entirely reliable, as somewhat similar symptoms, 

 often difficult to distinguish, are produced by 

 winter injury to various parts of the trunk, collar 

 and root, the peach borer, the root aphis, sour 

 soil, chlorosis, or even nitrogen starvation or soil 

 poverty. 



Frost collar girdle may even produce slightly 

 premature fruit as other girdling will do, but it 

 is not typical, for the yellows and the sjonptom 

 would not be reproduced in budding. True yellows 

 is often mixed up in the same orchards with frost 

 injury and other similar confusing symptoms. 

 Oftentimes, however, through examination of 



doubtful trees there will be found other symptoms 

 than yellows. 



Frost injuries, particularly, since 1903 and 

 1904, occurred from Michigan to New York and 

 New England in the yellows area. The eastern 

 part of the frost injury area overlaps a district 

 in which there has been an extensive outbreak of 

 yellows. This district extends from New England, 

 eastern and southern New York to Tennessee and 

 North Carolina. Frost injury has been severe 

 without accompanying yellows in western New 

 York, Ohio and Michigan. Yellows has been 

 severe without frost injury in New Jersey, Dela- 

 ware, Maryland, southern Pennsylvania to Ten- 

 nessee and North Carolina. The overlapping of 

 these two troubles in southern New York and 

 New England need not, therefore, be confusing. 

 0. L. Sheae, 

 Secretary-Treasurer 



SOCIETIES AND ACADEMIES 



THE CHEMIOAI, SOOrETT OF WASHINGTON 



The 198th meeting and annual smoker was held 

 at Fritz Reuters on Thursday, April 14. The 

 attendance at the smoker, which consisted of a 

 beefsteak dinner, was 57. The following papers 

 were read at the meeting: 

 The Effect of Drugs and Diet upon the Thyroid: 



Eeh) Hunt. 



Dr. Hunt discussed the changes in resistance 

 of animals to certain poisons caused by the ad- 

 ministration of various iodine compounds. Evi- 

 dence was presented that some of these changes 

 are caused by an effect upon the thyroid gland 

 and that certain iodine compounds have a selective 

 action upon this gland, that, in other words, they 

 are thyreotropic. Diet also was found to have 

 marked effects upon resistance to certain poisons; 

 some of these effects seem to be exerted, at least 

 in part, through the thyroid gland. 

 Contribution to the Knowledge of Phosplwric 



Acid: B. Heestein and Lyman F. Kebleb. 



Dr. Herstein said, in part, that a method having 

 been found to determine each of the three hydrates 

 of phosphorus pentoxid, when mixed with one 

 another, commercial glacial phosphoric acid and 

 metaphosphoric acid as prepared in the labora- 

 tory, were subjected to a study, the results of 

 which showed that: (1) contrary to the hitherto 

 accepted theory, metaphosphoric acid in changing 

 to the ortho-form first becomes pyrophosphorie 

 acid; (2) the percentage rate of inversion is very 

 little, if at all, influenced by dilution. 



Extensive tables and diagrams were prepared 

 in support of the above. 



